An Expression of Peace
The new United States Institute of Peace in Washington, D.C., will greet visitors to the nation’s capital with a sweeping white glass roof that evokes the image of a white dove of peace in flight.
The 154,000-sq-ft, five-story office building, located in the northwestern corner of the National Mall near the Theodore Roosevelt Memorial Bridge, respects the context of its historic surroundings while offering a striking modern addition to the National Mall.
Moshe Safdie Associates of New York designed the project as three buildings connected with glass-enclosed atria. The base buildings are clad in precast panels that blend with their neoclassical neighbors. Designers then juxtaposed that traditional look with two large-span undulating roofs.
“We see it as a gateway to the city from the Roosevelt Bridge,” says Paul Gross, principal in charge of the project with Moshe Safdie. “It respects the vocabulary of the National Mall and offers a symbolic gesture to the city.”
Before the visual statement could become a reality, construction crews had to get the base building in place. Clark Construction Group of Bethesda, Md., broke ground on the $108-million project in March 2008. The site required 95,000 cu yd of excavation, 65,000 cu yd of which was rock. The excavation support system required a 24- to 54-ft vertical cut with 134 soldier beams, 40 driven and 94 drilled; 22,000 sq ft of lagging; 13,000 sq ft of shotcrete; 271 drilled tiebacks; and 770 drilled rock bolts.
The site proved extremely sensitive. Despite the heavy amount of rock excavation required, crews had to minimize disruptions to tenants in neighboring buildings. The site is near the State Department and two U.S. Navy buildings, including one that is located 10 ft from the sheeting and shoring line.
“Blasting was a big concern during excavation,” says Mark Goodwin, project executive with Clark Construction.
Crews also built a temporary bypass for a 5- by 7-ft steam tunnel that ran through the site to service neighboring buildings. The steam line was ultimately reinstalled to pass through the buildings’ two-level, 100,000-sq-ft underground parking garage.
Additionally, a 100-year-old, 6-ft-8-in.-wide combined sewer overflow tunnel runs under the facility. Rather than creating a bypass with added pumping stations, Clark worked with the District of Columbia Water and Sewer Authority to reinforce the existing line. The crew slip-lined 300 lin ft of the 14-in.-thick brick-walled tunnel with a composite of concrete and fiberglass, then filled the annular space with foam grout.
Goodwin says the sewer work took nearly six months to complete because of the extremely careful excavation that was required around it.
“There was a lot of handwork involved,” he says.
The buildings’ foundations used a mix of spread footings with two lines of 12-ft drilled piers on each side of the sewer line, tied together with transfer beams.
The three five-story buildings are concrete clad with precast panels that blend with the neighboring limestone historic buildings.
As the structure reached the upper floors, the building’s dramatic visual statement began to take shape. The roof acts as its own structure atop the three USIP buildings. German firm Seele LP was added to the team in late 2006 for design assist of the steel-frame and glass-panel roof system.
Using building information modeling with Autodesk Revit and Rhino, designers devised two gridshell systems that would be built using preassembled pieces, each roughly 400 sq ft in surface area. The total surface area for the south roof is 12,000 sq ft and spans 80 ft between buildings. The north roof has 7,500 sq ft of surface area that spans 55 ft between buildings.
A framework of 4- by 8-in. hollow steel beams holds 1,500 triple-layered glass panels, the majority of which measure 4 by 4 ft except for custom-sized pieces along the edges.
The panels are designed to appear white at all times of day. Each panel is fritted on the exterior to give it a white appearance during the day. A white translucent membrane along the interior side of the panels gives it a white glow when illuminated from inside at night.